An integrated thin-film solar battery is generally formed by stacking a surface electrode layer made of a transparent conductive film, a photoelectric conversion layer made of a crystalline or amorphous semiconductor layer, and a back-surface electrode layer made of a metal thin film that serves as a reflector in this order on a translucent insulating substrate such as a glass substrate, which is a light receiving surface. In this type of thin-film solar battery, when the photoelectric conversion layer is made thin, its light conversion amount is decreased. Therefore, light is diffused by utilizing a surface electrode layer on an incident side and a back-surface electrode layer to increase an optical path length in the photoelectric conversion layer in order to increase the light conversion amount.
In relation to the thin-film solar battery having the above structure, there has been proposed a thin-film solar battery having a structure in which only a transparent conductive film is used as a back-surface electrode layer without using any metal thin film, and a highly-reflective white insulating layer is arranged on a back side of the transparent conductive film to achieve back-surface reflection having a high light diffusion effect (see, for example, Patent Literature 1). There has been further proposed a thin-film solar battery having a structure in which a transparent conductive film is formed on the entire surface of a photoelectric conversion layer and a comb-shaped metal electrode is arranged on the transparent conductive film to form a back-surface electrode layer, a translucent insulating film is formed on the comb-shaped metal electrode, and a back-surface reflective film is further formed on the translucent insulating film (see, for example, Patent Literature 2).